Field of the Invention
The invention relates to an adjusting apparatus, in particular for a lens in an optoelectronic transmitting/receiving device, and a method for adjusting the adjusting apparatus.
In optoelectronic transmitting/receiving devices for communication via optical fiber networks, one of the main problems consists in providing an optical connection between an optical fiber that is coupled on in a connection opening and a transmitting/receiving component. In the case of a laser module used for a transmitting device, the divergent laser beam of a laser diode is imaged by one or more lenses onto the end face of an optical fiber in such a way as to obtain a maximum coupling-in efficiency of the laser power into the optical fiber. When monomode optical fibers are coupled on, this is achieved by a single lens or a lens pair imaging the so-called spot size of the laser onto the light entry opening of the optical fiber. When two lenses are used, an aspherical lens is preferably used as the first lens owing to the laser radiation beam angle, which is usually large. Furthermore, in the case of the two-lens configuration, a collimated beam is often sought between the two lenses because the distance between the lenses is then non-critical. However, in the case of two-lens configurations, it is likewise possible for the first lens to generate a greatly enlarged intermediate image which is reduced again to the light entry opening of the fiber by the second lens. Semiconductor lasers for optical wide-area transmission systems emit at wavelengths of 1.3 xcexcm or 1.55 xcexcm and have spot radii of the order of magnitude of 1 xcexcm. Corresponding monomode optical fibers have spot radii of an order of magnitude of 5 xcexcm. In order to attain a high coupling efficiency, the first lens typically has to be adjusted and fixed with an accuracy of xc2x10.5 xcexcm in the x- and y-direction and of xc2x12 to 5 xcexcm in the z-direction with regard to the laser chip. For reasons of long-term stability, the fixing is usually carried out either by AuSn soldering or by laser welding. In order that the lens carriers can be produced with acceptable tolerances or a welding distortion when fixing the lens carrier can be corrected, it is particularly advantageous if targeted readjustment of the lens carrier and thus of the lens position can be carried out by laser pulses. Instead of the lens coupling, the optical fiber can also be directly coupled to the laser. The fiber end face is often melted or etched for this purpose, thereby producing a suitable lens profile on the optical fiber itself. In this case, the (locally metallized) optical fiber can be fixed e.g. by soldering on the laser-adjustable carrier.
Adjusting apparatuses for lenses and methods for adjusting them in which laser-adjustable actuating elements or actuators are used are already known. These known configurations are based on the temperature gradient mechanism (TGM), in which a laser beam impinging on the surface of a sheet-metal part introduces into the material, by melting the material on the surface, shrinkage stresses distributed non-uniformly over the sheet-metal thickness. As a result, the sheet-metal part flexes when cooling in the direction of the incident laser beam. For an adjustment operation with single-sided accessibility for the laser beam, this results in that adjustment can be effected reliably and in a defined manner only in one direction, in other words a distance can only be lengthened or shortened as a result of the bending. Using so-called actuators, however, it is also possible to realize further directions of movement in the case of only single-sided accessibility of the laser beam. In this case, an actuator is understood to be a three-dimensional sheet-metal structure on which, by introducing shrinkage stresses at specific places, it is possible to initiate defined movements of the actuator in different directions.
Published, European Patent Application EP 0 373 225 A1 describes an optoelectronic semiconductor device in which an optoelectronic semiconductor component is retained by a carrier block and, at the same time, a lens holder is fixed on the carrier block, a lens positioned opposite the optoelectronic component being mounted into the lens holder. The lens holder is preformed in such a way that it deforms in a desirable manner as a result of local exposure to a laser beam and, consequently, the position of the lens can be altered with regard to the optoelectronic component.
Furthermore, U.S. Pat. No. 5,572,895 describes a method for reciprocal adjustment of two members of one or more actuators, the members being connected via a bridge. In this method, too, laser energy is fed to the actuators at suitable places in order to bring about a desired adjustment.
Finally, U.S. Pat. No. 6,030,114 discloses a laser-adjustable fuse switch in which, according to the same principle as explained above, a pre-bent contact connection of a bimetal strip can be adjusted for calibration purposes by application of a laser beam.
These known methods have the disadvantage, however, that they generally permit only an empirical procedure during the adjustment by application of a laser beam. Moreover, the adjusting apparatuses are generally configured in such a way that they allow only coarse adjustment or fine adjustment. In many cases, the adjustment also does not exhibit long-term stability owing to the stresses incorporated during the laser processing.
It is accordingly an object of the invention to provide an adjusting apparatus and a method for its adjustment that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, which make it possible to carry out more targeted adjustment, in particular by providing coarse adjustment and fine adjustment.
With the foregoing and other objects in view there is provided, in accordance with the invention, an adjusting apparatus containing a stationary base plate, a movable carrier plate, and a number of actuating elements each having a first end, a second end, and a form that can be altered by local application of radiation energy. Each of the actuating elements is connected to the stationary base plate at the first end and to the movable carrier plate at the second end.
In an adjusting apparatus according to the invention, a number of actuating elements whose form can be altered by local application of radiation energy, preferably in the form of laser radiation, are connected to the stationary base plate at one of their ends and to the movable carrier plate at their other end. An optical component to be adjusted, such as a lens, can be mounted onto the carrier plate. In this case, the adjusting apparatus may also be part of an optoelectronic transmitting/receiving device which has an optoelectronic component such as a laser diode or a semiconductor photodetector and a connection opening for an optical fiber, and in which a carrier which retains the optoelectronic component is mounted on stationary parts of the adjusting apparatus, in which case, in the mounted and adjusted state, the optoelectronic component is exactly aligned with the lens and the light entry opening of the optical fiber.
The invention makes it possible to dispose a plurality of actuating elements of different configurations between the base plate and the carrier plate, which actuating elements make it possible to set the different degrees of freedom of the adjustment and of the movement of the carrier plate independently of one another. In particular, the invention makes it possible to dispose a plurality of actuating elements relative to one another in such a way that they act with different transmission, so that one actuating element can be utilized for the coarse adjustment and the second actuating element can be utilized for the fine adjustment.
The individual actuating elements can have different configurations, some of which are known per se in the prior art. By way of example, in a particularly simple embodiment, one actuating element may be configured as a linear, in particular bar-shaped actuating element whose length can be altered by application of a laser beam or the like along one direction. In this case, it may be provided that the actuating element is formed by a thin bar over its entire length, to which bar radiation energy can be applied at any point for the purpose of changing the length. Since this is generally not particularly stable, embodiments are usually chosen in which, between stabler sections of larger diameter (actuating element members), weak points of smaller diameter (webs) are formed at which the radiation energy is to be coupled in and at which the actual change of length takes place. Thus, an actuating element which acts only in one direction may have a number of two or more actuating element members which are disposed in the direction of the normal between the base plate and the carrier plate at a distance from one another and are each connected to one another by at least one web running in the direction of the normal. In this case, a plurality of webs may also be disposed parallel alongside one another. These webs may be so closely adjacent that even the exposure of only individual webs leads only to a change in length in the direction of the normal. However, the webs may also be spaced apart further from one another, so that a change in length brought about by the application of radiation to an individual web effects a movement of the carrier plate with a component in the direction of the normal and a transverse component with respect to the direction of the normal.
If the webs are spaced relatively far apart from one another in the embodiment described above, then an adjustment in two degrees of freedom can be carried out by an adjustment operation. It is more advantageous, by contrast, if the adjustment in the two degrees of freedom can be carried out by mutually independent adjustment operations. This is achieved by an adjusting apparatus in which one actuating element has a number of three or more actuating element members disposed between the base plate and the carrier plate, at least two actuating element members being disposed relative to one another in such a way that they are disposed in the direction of the normal between the base plate and the carrier plate at a distance from one another and are connected to one another by at least one web, and at least two other actuating element members are disposed relative to one another in such a way that they are spaced apart from one another in a lateral direction and are connected to one another by at least one web.
An essential aspect of the invention as mentioned above is that it opens up the possibility of constructing an adjusting apparatus in which a coarse adjustment can be carried out for one degree of freedom and then a fine adjustment can be carried out for the same degree of freedom. For this purpose, a first actuating element is connected to the carrier plate at a distance a from an outer edge of the carrier plate, and at a distance b therefrom, a second actuating element is connected to the carrier plate, so that the first actuating element can be used to carry out coarse adjustment and the second actuating element can be used to carry out fine adjustment with the transmission ratio a/(a+b).
Another equally simple actuating element is a two-dimensional, in particular plate-shaped actuating element that can change its form in two directions by a corresponding application.
Other more complex configurations of actuating elements are also conceivable, which can be mounted between the base plate and the carrier plate. By way of example, it is possible to use an actuating element which is essentially disclosed in European Patent Application EP 0 373 225 already mentioned and which has two planar sections which are disposed at an angle with respect to one another and are connected by an articulated joint. Such an actuating element can be formed from a sheet-metal part, like the other actuating elements described. The articulated joint at the bending point between the two planar sections can be formed in a simple manner by a reduced sheet-metal thickness and/or by cutouts in the sheet-metal part. A complete adjusting apparatus can be formed from two or more angular actuating elements of this type which are disposed on two opposite sides of the carrier plate, the bending points of the angular actuating elements preferably facing one another. Such an adjusting apparatus has the advantage that it can be used to carry out adjustment operations in different, mutually opposite directions, depending on the locations of the actuating elements to which the radiation energy is fed. In particular, for increasing the distance between the carrier plate and the base plate, the radiation energy is fed to those planar sections of the actuating elements which face the base plate, and for reducing the distance between the carrier plate and the base plate, the radiation energy is fed to those planar sections of the actuating elements which face the carrier plate.
As in this concrete embodiment, angular actuating elements of this type can be directly connected to the base plate and the carrier plate, in which case articulated joints can be provided at the connection points. The articulated joints being formed in a simple manner by a reduced sheet-metal thickness and/or by cutouts in the sheet-metal part.
However, it may also be provided that one actuating element is connected to an angle element which has two planar and bending-resistant sections which are disposed at an angle with respect to one another and are connected by an articulated joint, the angle element being connected to the base plate and the carrier plate by its planar sections and at least one of these connections having an articulated joint which is preferably likewise formed in the manner described above. In the case of such a construction, during the adjustment operation, the angular actuating element acts indirectly on the carrier plate by moving the planar sections of the angle element toward one another or away from one another.
One important application of the adjusting apparatus according to the invention concerns the adjustment of a lens mounted on the carrier plate relative to an optoelectronic component such as a semiconductor laser and a light entry or light exit face of an optical fiber. The adjusting apparatus can thus be part of an optoelectronic transmitting/receiving device which has a transmitting/receiving component, a connection opening for an optical fiber and a lens disposed between the connection opening and the transmitting/receiving component, the lens being mounted on a carrier plate of the adjusting apparatus according to the invention. In this case, the transmitting/receiving component and/or the fiber connection opening may be fitted to stationary parts of the adjusting apparatus, such as the base plate.
The different configurations of adjusting apparatuses enable defined, reproducible adjustment, so that, in the case of high numbers, the adjustment operation can also be automated. The required (lens) carriers can be produced cost-effectively for example by customary stamping and bending methods.
With the foregoing and other objects in view there is provided, in accordance with the invention, an adjustment method. The method includes providing an adjusting apparatus having a stationary base plate, a movable carrier plate, and a number of actuating elements each having a first end, a second end, and a form that can be altered by a local application of radiation energy. Each of the actuating elements is connected to the stationary base plate at the first end and to the movable carrier plate at the second end. A predetermined quantity of the radiation energy is fed to the actuating elements at predetermined locations.
In accordance with an added mode of the invention, there are the steps of providing at least one of the actuating elements to have at least two actuating element members disposed in a direction of a normal between the stationary base plate and the movable carrier plate at a distance from one another and are each connected to one another by at least one web; and feeding the radiation energy to the web.
In accordance with an additional mode of the invention, there are the steps of providing at least one of the actuating elements as an angular actuating element having two planar sections disposed at an angle with respect to one another and having articulated joints connected to the stationary base plate and the movable carrier plate; and feeding the radiation energy to the planar sections.
In accordance with another mode of the invention, there is the step of feeding the radiation energy to the planar sections of the actuating elements that face the stationary base plate for increasing a distance between the movable carrier plate and the stationary base plate.
In accordance with a further mode of the invention, there is the step of feeding the radiation energy to the planar sections of the actuating elements which face the movable carrier plate for reducing a distance between the movable carrier plate and the stationary base plate.
In accordance with a concomitant mode of the invention, there is the step of using a laser beam for supplying the radiation energy.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an adjusting apparatus and a method for its adjustment, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.